Metal conduit



D. INGALLS METAL CONDUIT Jan. 233, 1945.

Filed Oct. 9, 1942 Flu-In! a fi. y. r 4 -.4

IN V EN TOR.

,47'TOQNEY Patented Jan. 23, 1945 STATES PATENT OFFER METAL CONDUI'EDavid Kngalls, Westficld, N. 3., asslgnor to Tite= flex, inc, Newark, N.it, a corporation oi New Jersey 8 (Claims.

This invention relates to improvements in conduits which are madesubstantially entirely of metal, whereby the durability of the conduitis increased and the qualities of the conduit as a against radio waves,and in other ways, is improved. it'especially relates to flexible condmay have uses in other applications.

object of the invention is to increase the .ty of conduits comprisingcorrugated, tubes having structures or members outthe tubes to reeniorceor protect the same other purposes. ihe accomplishment of the presentinvention, s providing a flat. metal strip exea hell-sall about tube andlying flatly it. :-y lying flatly against the tube it is ed to err--ressthe strip is not interor interlaced with other strips so that it ield.iron: coming in contact with the tube lying smoothly upon the tube, the

true where the tube and conduit are flexible.

Where the tube is flexible the strip, by varying its breadth", thicknessor the pitchof its helix, or all of them, may provide means ofregulating flexibility and conversely the stiiiness, of the conduit, andthis is further object of the invention.

iurther object of the invention is to provide improved means forreeni'orcing the corrugated tube against elongation. This may beaccomplished by the helical strip lying flatly on the tube, beingsecured its ends to terminals to which the ends of the tube are secured,the strip by reason of its fiat-lying against the tube supplying a firmand unyielding means for this purpose.

A further object of the invention is to provide improved means forreenforcing the tube against twisting which is accomplished efficientlyand unyieldingly by the metal strip lying flatly against the tube andsecured at its ends to terminals to it oh the ends of the tube aresecured.

a. single helical strip about the tube as de scribed, however, will onlyreenforce the tube against twisting in one direction, it is, therefore,a further object or the invention to guard against torsional forces ineither direction by providing another fiat strip extending helicallyabout the tube and the inner helical strip lying flatly against it, theadded helical strip being wound in the opposite direction about the tubefrom the inner strip, the added strip passing outside the point byreason of underlying strip.

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inner flat-lying strip at all intersections so that the flat-lying or"the inner strip will not be interiered with, and the ends of each of thestrips are secured to terminals secured to the ends of the tube.

in the patent to L. H. Brinkman No. 1,198,392, granted September 12,1916, is described and shown a tube having a helical corrugation formedby helically disposing a metal strip having a central longitudinal foldor groove, the edges of adjacent convolutions being interfolded to forma fixed and tight seam. Such tube is flexible by the bending of thesides oi the corrugation toward and away from each other. This tube wasadmirable for many purposes, but it had certain vulnerabilities'amongwhich may be mentioned sliding in the joint or seam when the tube wassubjected to twisting, whereby the seam or joint might be loosened sothat it might not be fluidtight, or further injury might be done to thetube; also the tube was liable to increase in length when subjected tohigh internal pressure or outside longitudinal tensioning forces. It isa further object of the invention to reenforce and strength such a tubeagainst such vulnerabilities. This is done by placing a helical stripabout the tube, which strip lies flat against the corrugations, and whensuch strip is secured to terminals to which the end of the tube issecured, it provides a firm and inextensible reeniorcement against thevulnerabilities stated. The strip extending helically about the tube inone direction only will, however, reenforce against twisting in onedirection only. To accomplish reenforcement against twisting in eitherdirection it is necessary to employ a strip helically wound about thetube in the opposite direction and secured to terminals which aresecured to the end of the tube.

In order: to relieve against the vulnerabilities of the strip-formedtube as referred to, there was placed upon the tube a covering formed byinterwoven or braided metal strands about the tube, some or" the strandsof said covering being helically wound in one direction and other ofsaid strands being wound in the opposite direction about the tube, andinterlaced. These strands were secured at their ends to couplingssecured at the ends or the tube. Such conduit is set forth in the patentto L. H. Brinkman No. 1,340,818, granted May 18, 1920, with particularreference to Fig. 5 thereof. Such a conduit has performed most eficientand satisfactory service. It has been found, however, that this conduitcomprising the corrugated tube with the interlaced metal covering waslikely to be injured and its life shortened by wearing of the tubecorrugations by reason ofthe pressure against them of the interlacedcovering especially at the points of crossing of the interlaced strands.Such wear was liable to occur not only when the conduit was flexed, butalso when it was subjected to vibration. Such interlaced covering isdesirable as a finish for the tube and as a protection againstmechanical injury from without.

It is a further object of the invention to, in conduits of thischaracter, lessen or obviate the wear of the tube by the interlacedmetal covering. This is accomplished by interposing a flat strip lyingflatly against the tube corrugations between the interlaced orinterwoven outer covering and the corrugated tube whereby pressure ofthe intersection points of the strands and other points of the outercovering against the tube corrugation is relieved. Not only does suchinterposed strip guard-the corrugated tube against .wear, but when theinterposed strip is helically wound about the corrugated tube and hasits ends secured to the end terminals or couplings of 'such tube, itwill provide a more firm and inextensible means for preventinglengthening of the corrugated tube under high internal pressure or hightensile stresses, and it will also form a firm and unyielding means forpreventing twisting with consequent injury to the tube as above referredto.

It may, therefore, be said to be a further obiect of the invention toprovide means for efflciently and unyieldingly reenforcing the tubeagainst lengthening or twisting stresses. A strip helically wound in onedirection only, however, will guard against twisting in but onedirection only. Another flat strip helically wound about a corrugatedtube in the other direction and also secured to the terminal couplingswill reenforce against twisting in the other direction.

The use of one, two or more strips wound in the same or oppositedirections may be employed also for the purpose of regulating orpermitting the desired stiffness or flexibility of the conduit and alsoone or more strips may have the strip width or thickness or both variedfor the purpose last mentioned or for other reasons. When there aresuperposed strips between the outer interlaced covering and thecorrugated tube, each strip outside the one lying against the corrugatedtube, passes outside its next inner strip 50 that there is nointerlacing of the strips thereby rendering less liable wear upon thecorrugated tube and the strips lie more flatly and firmly upon the tube.

It is also to be observed that the outer interlaced covering provides ameans for holding the strip against the corrugated tube and prevents thestrips within the covering and about the corrugated tube from unwindingor unraveling when such strips are unsecured to end terminals, the outercovering being braided on at the same time that the strip is applied tothe tube and the braiding operation closely following up the winding ofthe strip.

While the invention has been above referred to as particularly useful inconnection with a conduit comprising a strip-formed,helically-corrugated tube in combination with an outer, braided orinterlaced, metal covering like that of the Brinkman Patent No.1,340,818, particularly as described with reference to Fig. 5 thereof,the invention may have useful application in connection with othercorrugated tubes, for instance as described in the patent to L. H.Brinkman No. 1,120,268, granted December 8, 1914, and also may flnd usein connection with corrugated tube without the outer braided covering.

Also while the strip or strips adjacent to and about the corrugated tubewill usually be of metal, they may, under some conditions, be ofsuitable non-metallic material, as, for instance, where the desiredfunction of such strip or strips interposed between a braided coveringand the corrugated tube is simply to relieve the pressure of thecovering on the tube, they may be of nonmetallic material such forinstance as braided Fiberglass.

While a flat strip lying flatly against the corrugations of the tube hasbeen referred to above, more than one such strip may be employed, thestrips being wound in the same direction and the ends of all the stripsmay be secured to the terminals secured to the ends of the tube. Undersuch circumstances it will be apparent that each of the strips willfulfill the objects and purposes of a strip as hereinbefore set forth.Also there may be a plurality of strips overlying the strip or stripsagainst the tube and wound in the opposite direction.

Other and ancillary objects of the invention will appear hereinafter andthe invention will be pointed out in the appended claims.

In the accompanying drawing which illustrates the invention;

Fig. 1 is a side elevation of a conduit embodying the invention, partlybroken away and partly in section;

Fig. 2 is a section on the line 2-2 of Fig. 1;

Fig. 3 is a side elevation, partly broken away and partly in section, ofa modified construction of conduit embodying the invention;

Fig. 4 is a section on the line 44 of Fig. 3;

Fig. 5 is a side elevation, on a reduced scale, partly broken away andpartly in section, of a length of the conduit as shown in Fig. 3 havingterminals secured to its ends; and

5 Fig. 6 is a fragmentary view, on a reduced scale, showing a sideelevation of a conduit having a plurality of flat lying strips againstthe tube and also a plurality of strips wound in the opposite directionand overlying the aforesaid strips, the conduit being partly brokenaway.

Referring to the drawing and first to Figs. 1, 2 and 3, the metal tube Ihaving the helical corrugations 2, may be of the construction of tube asdescribed and shown in the Brinkman Patent No. 1,198,392, this tubebeing formed as described in the said Brinkman, patent, of a helicallydisposed strip having alongitudinal fold or groove 3 with the edges of aconvolution being interfolded with the edges of adjacent convolutions asat 4 and 5, the tube then having its corrugation sides reflexed bycompressing the tube endwise.

Helically wound about the tube is a flat, metal strip 6 of substantiallyrectangular cross section and of greater width than thickness. Thisstrip may have its corners rounded so as to reduce the wearing orcutting effect of the edge upon the tube upon which it is wound or anyouter tube covering which may come in contact with it. The strip.

6 lies flatly against the corrugations 2 and the pitch of its helix isgreater than the pitch of the helical corrugation 2 so that the strip 6will bridge from one corrugation convolution to the next I whereby it isprevented from sinking into the depression between the corrugations andwearing sharply against the corrugation sides. The strip 8 is integralrather than being formed of a plurality of wires, whereby its wearingedges are reduced. Outside the fiat strip 6 is the braided metalcovering a comprising the interlaced or interwoven metal strips 8 and twhich are braided outside of the strip 5. Each of the strips'8 and 9 isflat, of substantially rectangular cross section and of greater widththan thickness, each strip being integral in cross section rather thanbein composed of a plurality of wires.

The strip lies flatly on the corrugation 2 and has less wearing eflectupon the corrugations than would be the case if the braided covering 7were placed directly on the corrugations. When the braided covering islaid directly upon the corrugations 2 there is inward pressure or proieions at the points of intersection of the interlaced strips of thebraided covering so that the inner strip at the intersection, or inwardprojection formed therein at that point, causes considerable wear uponthe corrugations of the inner tube, especiaily as the inner strip of thebraid, or projection formed therein, has edges liable to 'cut orincrease the wear on the inner tube. This may be illustrated byreference to Fig. 2 according to which the strip 9 of the outer braid ispressed in one direction by the middle one of the crossing strips 8 andoutwardly by the strips 8 on each side thereof. This results in theinward bend to in the strip 9 which will cause a wearing projection orwearing pressure upon the corrugations 2 as just referred to. It will beunderstood that this condition will occur at all crossings of theinterlaced strands of the braided covering '1 whether astrip s or astrip 9 is the inner one.

Byinterposing the helical strip 6 between the inner corrugated tube iand the braided covering 5, the braided covering is lifted away from thecorrugations 2 so that pressure therebetween, or projections causingwear of the corrugations by the braided covering, is avoided.

The conduit as a whole is flexible, the inner tube i flexing by relativemovement of the sides of its corrugations, which flexing is permitted bythe helical strip b and the braided covering i. It is during the flexingof the conduit that the wear referred to is most likely to occur, buteven where the conduit is in a use where it is not required to beflexed, serious wear may take place from vl= bration as where theconduit is used to house the ignition conductors of an internalcombustion engine. The construction of the invention, may, therefore, beuseful even when the conduit is not flexible or is not required to flex.

The strip d also provides a means for controlling the flexibility of theconduit as a whole by varying its pitch, width or thickness or all threeor any two of them. The pitch of the strip it should be made as great asis consistent with the desired characteristics of the tube and the useto which it is to be put, as the greater the pitch the less will be thetendency of the edges oi the strip to wear the corrugations 2 of theinner tube i.

It will be seen that the conduit as described, being of metal, willoperate as a shield against radio waves, as for instance where it isemployed as a conduit for an ignition conductor of an in= ternalcombustion engine, and when so employed the conduit may have itselectrical conductivity, which is important in such shielding, varied byvarying the cross section or material or both of the strip 6.

The braided outer covering may be applied to the conduit at the sametime that the helical strip i3 is applied to the tube, the braidingclosely following up the application of the spiral strip so that thespiral strip is held by the braid in position, and prevented fromunraveling, during manthe helical corrugation and bridges from one cor--rugation to the next.

Wound about the tube 1 and the strip Ii wound thereon, is the oppositelywound helical metal strip l2 passing outside of the strip II at alltheir crossings. The strip l2 also bridges from one convolution of thecorrugation 2 to the next and is of greater pitch than the helical tubeoorrugation, the pitch of the-helix of the strip I2 being approximatelyequal to that or the strip II and each of the strips II and i2 is ofless width than the strip 6.

Outside the tube and the two strips ll and I! wound thereon, and lyingagainst the strips, is the braided or interwoven metal outer covering 1,the same as the braided covering 1 of Fig. 1. The use of the two narrowhelical strips I] and 12 instead of the broad strip 5 of Fig. 1, changesthe flexibility of the conduit as is desirable for certain uses, whileat the same time protecting the tube 1' from undue pressure upon it atwearing points of the braided covering 1'.

In Fig. 5 is shown the conduit of Figs. 3 and 4 with terminals orcouplings l3 and 14 secured to its ends, the corrugated tube l', themetal strips I l and i2, and the outer braided covering 1 being enteredwithin the coupling H as shown and securely soldered therein, therebysecuring them to the coupling and to each other. At the other end of theconduit the tube 2', the strips II and i2 and the braided outer coveringI are entered within the coupling or terminal l3, the same as in thecoupling or terminal l4, and are securely soldered therein whereby theyare secured to the coupling and to each other. The ends of the tube,strips and braided covering having their ends secured together, and thestrips ii and 92 being oppositely helically' wound, reenforce theconduit against torsional stresses in both directions and also againsttensional or lengthening stresses applied either by high pressures uponthe interior of the tube or external tensioning force applied to thecouplings. In the case of the conduit structure of Fig. l, thecorrugated tube, the strip helically wound and lying flatly thereon andthe outer braided covering may have the ends of the tube, strip andcovering entered into a coupling and soldered securely therein at eachend of the conduit in a manner similar to the securing of the tube,strips and braided covering in the couplings as shown in Fig. 5.

In the case of Fig. 1, however, the helical strip 5 will only reen'forcethe conduit against twisting in one direction, but it will alsoreenforce the conduit against elongation.

Referring to Fig. 6, there is therein shown a. plurality of metal strips55 and it helically wound about and lying flat upon the corrugated metaltube 9" which is the same as the corrugated tube i and i of thestructures of Figs. 1, 3 and 5, said strips i5 and it being wound in thesame direction and opposite to the direction oi.

winding of the helical corrugation of the tube 8''.

Wound about the tube I" and the strips l5 and I6 thereon are th helicalstrips l1 and I8 wound in a direction opposite that of the strips l5 andI6 and being outside the strips 15 and I6 at all crossing points.Outside the strips I1 and I8 is the braided metal covering 1 the same asthe similar covering of the structures of Figs. 1, 3 and 5. The ends 'ofthe strips, the corrugated tube and the braided covering may be securedin a terminal at each end of the conduit as described in connection withFig. 5, and the strips l5, I6, I! and I8 will then function to reenforcethe conduit against torsional stresses in both directions and alsostresses tending to elongate the conduit. The plurality of strips lyingflatly against the corrugated tube and also a plurality of oppositelywound strips lying outside the tube contactin strips at all crossingpoints may be employed to regulate the flexibility of the conduit or forother purposes, by varying the size, number and relationship of thestrips to produce the desired result,

It will be obvious from the foregoing that any desired number of stripslying against the tube or any desired number of overlying strips may beemployed to achieve the desired conduit properties.

While the invention has been illustrated in what are considered its bestapplications it may have other embodiments without departing from itsspirit and is not, therefore, limited to the structures of the drawing.

What I claim is:

1. A conduit comprising in combination a corrugated, metal tube and aflat, metal strip helically disposed about said tube and lying flatlyagainst the corrugations of said tube.

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2. A conduit comprising in combination a metal tube having a helicalcorrugation and a flat, metal strip helically disposed about said tubeand lying flatly against the corrugations of said tube, said helicalstrip being of greater pitch than the helical corrugation of said tube.

3. A conduit comprising in combination a metal tube having a helicalcorrugation and a flat, metal strip helically disposed about said tubeand lying flatly against the corrugations of said tube, the direction ofsaid helical strip being opposite to that of said helical corrugation.

4. A conduit comprising in combination a corrugated, metal tube and aplurality of flat, metal strips helically disposed about said tube andlying flatly against the corrugation of said tube.

5. A conduit comprising in combination a corrugated, metal tube, a flat,metal strip helically disposed about said tube and lying flatly againstthe corrugations of said tube and a braided metal covering about saidtube and strip.

6. A conduit comprising in combination a corrugated, metal tube and aflat strip helically disposed about said tube and lying flatly againstthe corrugations of said tube.

7. A conduit comprising in combination a corrugated, metal tube, a flatstrip helically disposed about said tube and lying flatly against thecorrugations of said tube and a braided metal covering about said tubeand strip,

8. A conduit comprising in combination a corru ated, metal tube, aplurality of flat strips helically disposed about said tube and lyingflatly against the corrugations of said tube and a braided, metalcovering about said tube and strips.

DAVID INGALLS.

